Electrified vehicles, such as hybrid electric vehicles (HEV's), plug-in hybrid electric vehicles (PHEV's), battery electric vehicles (BEV's), or fuel cell vehicles differ from conventional engine vehicles in that they are powered by one or more electric machines (i.e., electric motors and/or generators) instead of or in addition to an internal combustion engine. High voltage current for powering the electric machines is typically supplied by a high voltage traction battery pack.
Electrified vehicle battery packs are made up of multiple battery modules. The battery cells of each battery module may need to be thermally managed to remove excess heat out of the battery pack. Some battery packs are air cooled and typically push or pull pressurized air through a battery pack inlet and outlet. As air flows through the battery pack toward the outlet, a gradient of temperature and pressure may be created. This may cause the battery cells to age at varying rates.